1. Field of the Invention
The present invention relates to an image delivering apparatus, and, more particularly to an image delivering apparatus suitable for converting character images into vector data and displaying the vector data on various potential terminal monitors.
2. Description of the Related Art
In recent years, image data input from an image input device such as a scanner is fed to a calculator and processed according to the purpose. For example, after segmenting bitmapped image data input from the image input device, the calculator extracts edge lines and performs line segment approximation of the edge lines, to convert the input data into vector format that can be easily processed (see, for example, Japanese Patent Application Laid-open No. H5-334430).
Vector format refers to a data representation format in which data is represented in terms of coordinates of the start points and end points of the segments on the image, the segments being obtained by line segment approximation. Data volume markedly reduces when the data is converted into vector format, which is desirable from the point of view of the calculation process. However, if the image to be processed contains character data, it becomes important whether the character image displayed after the conversion into vector format is legible.
A method in which the edge lines are traced, extracted, and subjected to polyline approximation is widely used as a method for converting a complete image that includes characters into vector data (see, for example, Japanese Patent Application Laid-open No. H5-290161). However, character distortion occurs when the image after the conversion process is displayed in reduced size, and problems such as difficulty in deciphering the characters are encountered. To avoid such problems, the character data included in the image is separated from the image by feature extraction, character recognition is carried out by pattern matching, after which coding is performed using a combination of position coordinates and character codes (see, for example, Japanese Patent Application Laid-open No. H6-76035).
However, if coding is performed via character recognition, reliability of the information included in the character image becomes questionable when character recognition is not performed accurately. Methods to counter such problems are also proposed in which character images that are likely to be falsely recognized are not converted into character code data, but are output as character images (such as raster data) only. However, in such cases, an extreme difference in legibility and visual appeal of characters results between the character code data and the character image, which can be visually annoying. In an image in which characters are in the form of character codes, there is no proportional change in the character size when the image size is scaled up or down. Regardless of whether characters are stored as character images or character codes, if incorporation of processes such as scaling the size up or down at the time of delivery is envisaged, it would entail adding a restoration process, making the delivery process complex.
In recent years, many vector conversion methods have been proposed and a faithful reproduction of the original image is possible when a general image is converted into vector data. However, as mentioned earlier, in case of character images, maintaining the legibility of character images after vector conversion is an important issue, and the vector conversion process for obtaining the best display is determined depending on factors such as the character image and the display environment.
For example, in cases that require the image to be displayed in reduced size due to reasons such as small monitor of the display medium, if the earlier mentioned method that converts edge lines into vector data is used, there is character distortion. To prevent character distortion, measures such as converting the skeleton line into vector data and then displaying the characters as characters having line width of one dot are required. On the contrary, if the method that converts edge lines into vector data is used when the character size to be displayed is somewhat large, the shape of characters in the image can be faithfully reproduced and visual appeal is improved.
Thus, by selecting a vector conversion process that is appropriate for the character image, vector data with excellent legibility and visual appeal can be obtained, and various processes can be performed without encountering problems when converting characters into codes via character recognition described above.